Posts Tagged ‘md5’

JavaScript MD5 hash for air.FileStream

This is the MD5 file hash used in progTools.

You can copy and paste the code below or get it via. bitbucket.

The code builds upon Paul Johnston’s MD5 implementation and you’ll need to include his code first.

<!-- Paul Johnston's MD5 implementation -->
<script type="text/javascript" src="tools/md5/md5.js"></script>

<!-- Additional MD5 functions for working on air.FileStream; requires Paj's md5.js -->
<script type="text/javascript" src="tools/md5/md5_file.js"></script>

core_md5_ex() is a modified/hacked version of the original core_md5() to allow for progressively processing chunks of data, instead of doing it all in one go.

// modified version of Paul Johnston's MD5 implementation
function core_md5_ex(x, len, abcd_start, append_padding, total_len)
{
/* append padding */
if (append_padding) {
    x[len >> 5] |= 0x80 << ((len) % 32);
    x[(((len + 64) >>> 9) << 4) + 14] = total_len*8;
}

var a = abcd_start[0];
var b = abcd_start[1];
var c = abcd_start[2];
var d = abcd_start[3];

for(var i = 0; i < x.length; i += 16)
{
var olda = a;
var oldb = b;
var oldc = c;
var oldd = d;

a = md5_ff(a, b, c, d, x[i+ 0], 7 , -680876936);
d = md5_ff(d, a, b, c, x[i+ 1], 12, -389564586);
c = md5_ff(c, d, a, b, x[i+ 2], 17, 606105819);
b = md5_ff(b, c, d, a, x[i+ 3], 22, -1044525330);
a = md5_ff(a, b, c, d, x[i+ 4], 7 , -176418897);
d = md5_ff(d, a, b, c, x[i+ 5], 12, 1200080426);
c = md5_ff(c, d, a, b, x[i+ 6], 17, -1473231341);
b = md5_ff(b, c, d, a, x[i+ 7], 22, -45705983);
a = md5_ff(a, b, c, d, x[i+ 8], 7 , 1770035416);
d = md5_ff(d, a, b, c, x[i+ 9], 12, -1958414417);
c = md5_ff(c, d, a, b, x[i+10], 17, -42063);
b = md5_ff(b, c, d, a, x[i+11], 22, -1990404162);
a = md5_ff(a, b, c, d, x[i+12], 7 , 1804603682);
d = md5_ff(d, a, b, c, x[i+13], 12, -40341101);
c = md5_ff(c, d, a, b, x[i+14], 17, -1502002290);
b = md5_ff(b, c, d, a, x[i+15], 22, 1236535329);

a = md5_gg(a, b, c, d, x[i+ 1], 5 , -165796510);
d = md5_gg(d, a, b, c, x[i+ 6], 9 , -1069501632);
c = md5_gg(c, d, a, b, x[i+11], 14, 643717713);
b = md5_gg(b, c, d, a, x[i+ 0], 20, -373897302);
a = md5_gg(a, b, c, d, x[i+ 5], 5 , -701558691);
d = md5_gg(d, a, b, c, x[i+10], 9 , 38016083);
c = md5_gg(c, d, a, b, x[i+15], 14, -660478335);
b = md5_gg(b, c, d, a, x[i+ 4], 20, -405537848);
a = md5_gg(a, b, c, d, x[i+ 9], 5 , 568446438);
d = md5_gg(d, a, b, c, x[i+14], 9 , -1019803690);
c = md5_gg(c, d, a, b, x[i+ 3], 14, -187363961);
b = md5_gg(b, c, d, a, x[i+ 8], 20, 1163531501);
a = md5_gg(a, b, c, d, x[i+13], 5 , -1444681467);
d = md5_gg(d, a, b, c, x[i+ 2], 9 , -51403784);
c = md5_gg(c, d, a, b, x[i+ 7], 14, 1735328473);
b = md5_gg(b, c, d, a, x[i+12], 20, -1926607734);

a = md5_hh(a, b, c, d, x[i+ 5], 4 , -378558);
d = md5_hh(d, a, b, c, x[i+ 8], 11, -2022574463);
c = md5_hh(c, d, a, b, x[i+11], 16, 1839030562);
b = md5_hh(b, c, d, a, x[i+14], 23, -35309556);
a = md5_hh(a, b, c, d, x[i+ 1], 4 , -1530992060);
d = md5_hh(d, a, b, c, x[i+ 4], 11, 1272893353);
c = md5_hh(c, d, a, b, x[i+ 7], 16, -155497632);
b = md5_hh(b, c, d, a, x[i+10], 23, -1094730640);
a = md5_hh(a, b, c, d, x[i+13], 4 , 681279174);
d = md5_hh(d, a, b, c, x[i+ 0], 11, -358537222);
c = md5_hh(c, d, a, b, x[i+ 3], 16, -722521979);
b = md5_hh(b, c, d, a, x[i+ 6], 23, 76029189);
a = md5_hh(a, b, c, d, x[i+ 9], 4 , -640364487);
d = md5_hh(d, a, b, c, x[i+12], 11, -421815835);
c = md5_hh(c, d, a, b, x[i+15], 16, 530742520);
b = md5_hh(b, c, d, a, x[i+ 2], 23, -995338651);

a = md5_ii(a, b, c, d, x[i+ 0], 6 , -198630844);
d = md5_ii(d, a, b, c, x[i+ 7], 10, 1126891415);
c = md5_ii(c, d, a, b, x[i+14], 15, -1416354905);
b = md5_ii(b, c, d, a, x[i+ 5], 21, -57434055);
a = md5_ii(a, b, c, d, x[i+12], 6 , 1700485571);
d = md5_ii(d, a, b, c, x[i+ 3], 10, -1894986606);
c = md5_ii(c, d, a, b, x[i+10], 15, -1051523);
b = md5_ii(b, c, d, a, x[i+ 1], 21, -2054922799);
a = md5_ii(a, b, c, d, x[i+ 8], 6 , 1873313359);
d = md5_ii(d, a, b, c, x[i+15], 10, -30611744);
c = md5_ii(c, d, a, b, x[i+ 6], 15, -1560198380);
b = md5_ii(b, c, d, a, x[i+13], 21, 1309151649);
a = md5_ii(a, b, c, d, x[i+ 4], 6 , -145523070);
d = md5_ii(d, a, b, c, x[i+11], 10, -1120210379);
c = md5_ii(c, d, a, b, x[i+ 2], 15, 718787259);
b = md5_ii(b, c, d, a, x[i+ 9], 21, -343485551);

a = safe_add(a, olda);
b = safe_add(b, oldb);
c = safe_add(c, oldc);
d = safe_add(d, oldd);
}

return Array(a, b, c, d);
}

What’s changed is:

  • We pass in the starting values (which is the current hash on the data thus far, minus the necessary padding)
  • We use a variable to determine whether or not to append padding to the input; this is only done when processing the last block on data read from the stream.

hex_md5_stream() is the function which processes the stream: reading in chunks, transforming the bytes in inBytes into an array 4-byte WORDs, and calling core_md5_ex() with the necessary data.

function hex_md5_stream(inStream)
{
    
var abcd_start = new Array();
    abcd_start.push(1732584193);
    abcd_start.push(-271733879);
    abcd_start.push(-1732584194);
    abcd_start.push(271733878);
    
    
var inBytes = new air.ByteArray();
    
var appendPaddingToBlock = false;
    
var totalLen = 0;
    
    
while (inStream.bytesAvailable > 0)
    {
        inStream.readBytes(inBytes, 0, Math.min(8192, inStream.bytesAvailable));        
        
if(inBytes.length < 8192)
        {
            appendPaddingToBlock =
true;
        }
        
        totalLen += inBytes.length;
        
        bin =
new Array();
        
for(var i = 0; i < inBytes.length * 8; i+=8)
            bin[i>>5] |= (inBytes[i>>3] & 0xff) << (i%32);
        
        abcd_start = core_md5_ex(bin, inBytes.length*8, abcd_start, appendPaddingToBlock, totalLen);
        inBytes.clear();
    }
    
    
return binl2hex(abcd_start);    
}

Here’s the top-level view of how it works:

var inStream = new air.FileStream();
                
var file = new air.File();
file.url =
"file:///" + filename;                

inStream.open(file, air.FileMode.READ);
var md5result = hex_md5_stream(inStream);                 
inStream.close();             

progTools and Adobe Air

I made a little app to get my feet wet with Adobe Air. progTools just packages together a few common functions I find myself using frequently. You can get it my clicking the install badge (one of the very cool aspects of Adobe Air) below.

Please upgrade your Flash Player This is the content that would be shown if the user does not have Flash Player 9.0.115 or higher installed.

(h/t to Peter Elst for the AIR Badge WordPress plugin)

What’s offered:

  • Conversion to/from a Unix timestamp
  • MD5 hash on a string
  • MD5 hash on a file
  • SHA1 hash on a string

progTools 1.2

Not too impressive, and only the MD5 file hash really utilizes a desktop feature of the Air framework, but it is somewhat useful and, at least in my case, I won’t end up going to Paj’s Home to use the javascript md5 implementation demo quite as often. Note, Paj’s MD5 library was used and I slightly modified core_md5() for the file hash to deal with hashing successive blocks. I’ll post the code soon.

I initially dismissed Air, back when it was Apollo, as I didn’t see the value in having yet another proprietary framework which didn’t really offer much beyond what was capable within a browser, aside from local file access. A few additions to the framework and a few realizations on my part have shifted my views:

  • Air supports HTML/CSS for layout and styling. Looking into cross-platform GUI frameworks, I’ve played around with WinForms (cross platform with Mono), Qt, Gtk, and wxWidgets. I’ve been disappointed to various degrees with all of them. It hit me that the most flexible and powerful cross-platform layout and styling framework out there is the HTML/CSS combo. It’s not perfect (e.g. floats, vertical centering) but it’s pretty damn good.
  • Support in Air 2 for sockets and interaction with native applications. This vastly opens the field for the types of applications possible with Air.
  • Market support from Adobe. The Air Marketplace is perhaps not too impressive, but it’s a major step in the right direction for desktop apps. Both Microsoft and Apple have their own stores planned, but with the success of such catalogs on smartphones for years now, why did it take so long to figure it out?
  • Install badges. They’re cool and important as they provide a bridge between the web and the desktop. Odd, but it seems Adobe more-so than Microsoft or Apple seems to understand the web-desktop relationship. Again, why is Adobe, a company that was fairly divorced from the desktop application space, the first to figure out that this was something important or at least the first to actually build it.

Now it’s not all sunshine and roses. Making an HTML/AJAX app in Air brings up a problem every AJAX developer has likely faced at some point. Javascript is slow… very slow. JavaScriptCore/Nitro, V8, Chakra, Tracemonkey… it doesn’t really matter (though performance improvements are being made), once your volume of data grows you’ll cringe at how slow things become. Coming from C++, C#, or even PHP, it’s painful to witness. In progTools a file only a few megabytes large will noticeably stall the application (I didn’t do the call asynchronously, but that’s besides the point). ActionScript is perhaps better and interop to a native executable could also alleviate the issue, but ultimately I’d simply like a faster JavaScript engine.

A second issue, relevant but not specific to Adobe Air, is code signing; you’ll notice the scary warning when installing progTools. Code signing is bullshit. Expensive bullshit. Yet, every platform developer is requiring it due to some misguided attempt at security. If you want to install progTools, the chain of trust is between me » this web server » you. Sticking a certificate authority in this chain is nonsense – a typical user will not know the CA and cannot establish any level of trust with some random, corporate CA.

Coding signing simply punishes small developers and establishes a new industry to leech from our wallets. In addition, as this user on StackOverflow asserts, it may well hamper the success of Air:

When you visit a site that lets you download an AIR app, it pops up big red screaming warnings about the imminent trashing of your computer, the theft of your identity and a life of torment[1]. Unless, of course, all the bedroom programmers decide to cough up the ongoing cost of certification.

User encouragement FAIL. Hobby developer encouragement FAIL. Technophobe terrorficiation avoidance FAIL.

I love AIR, but I don’t know what they were thinking with the installer. Laywers’ office moved closer to the developers’ over at HQ or something?

Anyways, I’m done ranting. I’ll eventually suck it up and get a certificate as I’m powerless to do anything else.

As for Air, I’ve just scratched the surface, but I’m impressed.

oh, and if you’d like to see something added to progTools, just let me know.